By doing that you're effectively turning these websites into 4chan. Can you imagine a website like Hacker News if no moderation was possible, nobody could get banned and nothing could be removed without a court order? You'd just have every thread spammed by bots.

That's the problem with unmoderated online discourse, cheap inflammatory posts are easy to make and draw a lot of attention while in-depth analysis takes time to write and to read. Why bother coming up with a clever retort if you can just spam "no u" and "fuck off" until those people are driven away?

In my experience no moderation doesn't result in more varied opinions, instead it turns into an echo chamber where the bullies take over. Again, look at 4chan or some of the most popular, less moderated subreddits. It's pretty crap.

The ideal state of affairs is when you can have multiple platforms, moderated in different ways as they compete for customers in a free (i.e. competitive) market, where such moderation, or lack thereof, is a part of their pitch to new customers.

But we let companies monopolize whole segments of the market. And then every such segment becomes a vast echo chamber of whatever the prevailing public opinion at the moment is.